In these units it is desirable to operate with a single valve seat associated with a respective closure element which has both the function of shutting off the gas flow (ON/OFF) and the function of adjusting the flow to achieve the water temperature desired by the user. In this connection, the valve unit has a knob adjustment device operatively connected to the closure element by a control member with which the user can enable the function of lighting a pilot burner or of shutting off the gas-flow (OFF) and, in addition, can select a preselected water-temperature value.
When the above-mentioned functions are incorporated in a single device, it is also desirable to be able to perform these functions at most by a single rotation of the knob, in order to achieve quicker and easier use by the user. However, in addition to the angular temperature-selection band (normally an adjustment within the range between approximately 30° C. and 70° C. is required), it is therefore necessary also to provide an angular band on the knob for regulating the shut-off (OFF) and pilot-burner lighting points. This therefore reduces the angular band available for temperature selection, which translates into a lower degree of resolution within the above-mentioned range of between approximately 30° C. and 70° C. such that the user cannot adjust the temperature with a sensitivity, for example, with variations on the order of one degree centigrade in the preselected temperature values.
The problem which the present invention solves is that of providing a knob adjustment device which is designed structurally and functionally so as to overcome the disadvantages explained with reference to the prior art mentioned.